Effects of state-wide implementation of the Los Angeles Motor Scale for triage of stroke patients in clinical practice

Background The prehospital identification of stroke patients with large-vessel occlusion (LVO), that should be immediately transported to a thrombectomy capable centre is an unsolved problem. Our aim was to determine whether implementation of a state-wide standard operating procedure (SOP) using the Los Angeles Motor Scale (LAMS) is feasible and enables correct triage of stroke patients to hospitals offering (comprehensive stroke centres, CSCs) or not offering (primary stroke centres, PSCs) thrombectomy. Methods Prospective study involving all patients with suspected acute stroke treated in a 4-month period in a state-wide network of all stroke-treating hospitals (eight PSCs and two CSCs). Primary endpoint was accuracy of the triage SOP in correctly transferring patients to CSCs or PSCs. Additional endpoints included the number of secondary transfers, the accuracy of the LAMS for detection of LVO, apart from stroke management metrics. Results In 1123 patients, use of a triage SOP based on the LAMS allowed triage decisions according to LVO status with a sensitivity of 69.2% (95% confidence interval (95%-CI): 59.0–79.5%) and a specificity of 84.9% (95%-CI: 82.6–87.3%). This was more favourable than the conventional approach of transferring every patient to the nearest stroke-treating hospital, as determined by geocoding for each patient (sensitivity, 17.9% (95%-CI: 9.4–26.5%); specificity, 100% (95%-CI: 100–100%)). Secondary transfers were required for 14 of the 78 (17.9%) LVO patients. Regarding the score itself, LAMS detected LVO with a sensitivity of 67.5% (95%-CI: 57.1–78.0%) and a specificity of 83.5% (95%-CI: 81.0–86.0%). Conclusions State-wide implementation of a triage SOP requesting use of the LAMS tool is feasible and improves triage decision-making in acute stroke regarding the most appropriate target hospital.

Real-World Field Performance of the Los Angeles Motor Scale as a Large Vessel Occlusion Screen: A Prospective Muticentre Study

<b><i>Background:</i></b> The Los Angeles Motor Scale (LAMS) is a 3-item, 0-to-5-point motor stroke-deficit scale derived from the Los Angeles Prehospital Stroke Screen. We assessed the predictive validity (for interventions performed and discharge disposition) of the LAMS performed in the field by paramedics in a geographic region of over 5,200 km², covering both rural and urban areas. <b><i>Methods:</i></b> We analyzed data gathered from Phase I of the LIT-PASS study (Large Vessel Occlusion Identification Through Prehospital Administration of Stroke Scales) which included all patients with suspected acute cerebrovascular disease, as assessed by the Balance, Eyes, Face, Arm, Speech, Terrible Headache/Time to Call 911 (BE-FAST) test. <b><i>Results:</i></b> Among 1,906 patients with median age 72 years (interquartile range [IQR] 60–81), 53% were female with a median on-scene time of 15 min (IQR 12–19). C statistics for the interventions of mechanical thrombectomy, alteplase administration, computed tomography angiography, and perfusion imaging were 0.681, 0.643, and 0.680, respectively. The cut point for predicting these 3 interventions was confirmed to be LAMS ≥ 4. LAMS ≥ 4 had sensitivity 0.730 (0.661–0.790) and specificity 0.570 (0.539–0.601) for mechanical intervention (endovascular thrombectomy, coiling, or clipping) and relative risk of 2.98 (2.19–4.07) for in-hospital death. <b><i>Conclusions:</i></b> This real-world field study validates the LAMS as an effective tool for prehospital assessment of suspected strokes in determining transport decisions, with predictive validity for interventions performed.

Abstract WP277: The Los Angeles Motor Scale is an Effective Tool for Triaging Patients in the Prehospital Setting

Introduction: The Los Angeles Motor Scale (LAMS) is a 3-item scale to identify motor deficits. This can identify severe strokes in the field so that patients can be transported appropriately. Methods: Prospective observational cohort study based in a county EMS system. Patients transported for stroke had a LAMS administered in the field. Outcome data from individual receiving hospitals collected within 45 days of the event. Results: Our cohort (n=2374) had a median age of 72 and was 51% female. 19% had LAMS 0, 14% LAMS 1, 13% LAMS 2, 17% LAMS 3, 16% LAMS 4, and 21% had LAMS 5. We generated three receiver operating characteristic curves for the interventions of mechanical intervention, tPA, and CTA perfusion imaging, with C statistics of .706, .632, and .668 respectively. All three models were significant using the likelihood ratio test, p < .0001. In all three models, the cut point was a LAMS of 4. Accordingly, a high LAMS was defined as 4 or 5, whereas a low LAMS was defined as <4. In the following table, all associations were significant with p < .0001 using the likelihood ratio test. The median NIHSS at hospital arrival was 6, IQR 2-13. For low LAMS it was 4 (IQR 1-8), and for high LAMS it was significantly greater at 13, IQR 7-21, p <.0001 using Wilcoxon’s rank-sum test. At hospital discharge, median NIHSS was 2, IQR 0-7. For low LAMS it was 1 (IQR 0-5), for high LAMS it was significantly greater at 5 (IQR 1-14.75), p < .0001 using Wilcoxon’s rank-sum test. Median NIHSS improvement was 2 points, p < .0001 (Wilcoxon signed-rank test). The differences were significant with p < .0001 for both low LAMS and high LAMS patients individually (Wilcoxon signed-rank test). Low LAMS patients had a median improvement of 1.5 points. High LAMS patients had a significantly greater median improvement of 4 points (p < .0001 using Wilcoxon rank-sum test), likely because they generally started out in worse condition. Conclusion: The LAMS is a powerful prehospital predictor of intervention and outcomes after acute stroke.

Abstract TMP61: Improved Routing of Comprehensive Stroke Center Appropriate Patients via Mobile Stroke Unit Conclusive Field Diagnosis

Background: Mobile Stroke Units (MSUs) are capable of rapid initiation of intravenous thrombolysis and have the potential to improve acute stroke patient routing by providing conclusive imaging diagnosis of LVO (arterial sequences) and intracranial hemorrhage (parenchymal/extraparenchymal sequences). However, the incremental increase in diagnostic accuracy and effect on patient disposition have not been well delineated. Methods: Consecutive transports in a regionally-deployed MSU from September 2017-August 2019) were analyzed, comparing patient routing that would have occurred under standard ambulance protocols to routing and process outcomes after CT/CTA MSU imaging. Standard ambulance regional routing policy was direct to nearest PSC if Los Angeles Motor Scale (LAMS) 0-3 and direct to nearest CSC within 30m if LAMS 4-5. Results: Among 83 MSU transports, final diagnosis was acute cerebral ischemia in 68% and intracranial hemorrhage in 10%. Among 57 acute cerebral ischemia patients, Los Angeles Motor Scale (LAMS) score was 0-3 in 65% and 4-5 in 35%. All (100%) of patients with ICA/M1 occlusions had LAMS score 4-5. However, among patients with expanded range endovascular target occlusions (M2, basilar), LAMS scores were 0-3 in 56%, and MSU imaging permitted improved routing. Among 8 intracranial hemorrhage patients (2 IPH, 5 SDH, 1 SAH), MSU imaging permitted improved direct-to-CSC routing in the 62% of patients with LAMS scores 0-3. Among all MSU admissions, 15% (13) were rerouted based solely upon in-vehicle imaging, including 7% for radiographically proven endovascularly treatable occlusion, 7% for neurosurgical/NICU intracranial hemorrhage care, and 1% for neurosurgical tumor care. Transport times for re-routed patients was median 12 minutes, compared to closest stroke center median 6 minutes. Conclusion: More than 1 in 7 MSU evaluations result in improved routing of comprehensive stroke center-appropriate patients directly to a CSC facility, including AIS patients potentially eligible for thrombectomy, intracranial hemorrhage patients, and acutely-presenting brain tumor patients. In addition to speeding start of intravenous thrombolysis, MSUs can substantially improve timely access to CSC care.

Abstract TP242: The Los Angeles Motor Scale Outperforms the Vision, Aphasia, Neglect Test as a Prehospital Stroke Scale

Introduction: In the prehospital setting, it is important to identify which patients need to be sent to a comprehensive stroke center. Methods: This IRB-approved prospective study included all patients transported for stroke by our EMS system from December 2018-May 2019. Patients were administered the Los Angeles Motor Scale (LAMS) and vision, aphasia, neglect (VAN) test by paramedics prior to hospital arrival. LAMS 4 or 5 was considered high for the purposes of our study. Patients were considered VAN positive if they were deficient in any of the three areas it tests. Results: Our cohort (n=480) was 50% male. Median age was 72, IQR 62-81 and range 13-108 years. The LAMS/VAN breakdown (n=378 patients who received both) was as follows: Low LAMS/Negative VAN: 32% High LAMS/Negative VAN: 10% Low LAMS/Positive VAN: 38% High LAMS/Positive VAN: 20% 68% of patients had either high LAMS or positive VAN. 26% received CTA perfusion imaging, 14% received tPA, and 7% received mechanical intervention. 9% were hemorrhagic strokes, 43% ischemic, and 11% TIAs. The median National Institutes of Stroke Score (NIHSS) at hospital arrival was 6, with IQR 2-13 and range 0-36. 50% of patients were discharged home and 5% expired. Table 1: relative risk (if applicable) and p-values associated with certain outcome-scale combinations, calculated using Fisher’s exact test or Wilcoxon’s rank-sum test (NS = not significant). In predicting mechanical intervention, LAMS had sensitivity 87% and specificity 72%, VAN had sensitivity 73% and specificity 41%, LAMS or VAN had sensitivity 96% and specificity 31%, LAMS and VAN had sensitivity 62% and specificity 82%. Conclusions: The LAMS is more effective than the VAN for general prehospital usage. Combining the two scales results in higher sensitivity at the cost of specificity in predicting mechanical intervention, which may be useful so that all potentially eligible patients for mechanical intervention can be sent to a comprehensive stroke center.